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55 lines
1.6 KiB
C
55 lines
1.6 KiB
C
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/*
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* USB Compaq iPAQ driver
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*
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* Copyright (C) 2001 - 2002
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* Ganesh Varadarajan <ganesh@veritas.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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*/
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#ifndef __LINUX_USB_SERIAL_IPAQ_H
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#define __LINUX_USB_SERIAL_IPAQ_H
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/*
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* Since we can't queue our bulk write urbs (don't know why - it just
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* doesn't work), we can send down only one write urb at a time. The simplistic
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* approach taken by the generic usbserial driver will work, but it's not good
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* for performance. Therefore, we buffer upto URBDATA_QUEUE_MAX bytes of write
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* requests coming from the line discipline. This is done by chaining them
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* in lists of struct ipaq_packet, each packet holding a maximum of
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* PACKET_SIZE bytes.
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*
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* ipaq_write() can be called from bottom half context; hence we can't
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* allocate memory for packets there. So we initialize a pool of packets at
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* the first open and maintain a freelist.
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*
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* The value of PACKET_SIZE was empirically determined by
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* checking the maximum write sizes sent down by the ppp ldisc.
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* URBDATA_QUEUE_MAX is set to 64K, which is the maximum TCP window size.
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*/
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struct ipaq_packet {
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char *data;
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size_t len;
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size_t written;
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struct list_head list;
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};
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struct ipaq_private {
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int active;
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int queue_len;
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int free_len;
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struct list_head queue;
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struct list_head freelist;
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};
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#define URBDATA_SIZE 4096
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#define URBDATA_QUEUE_MAX (64 * 1024)
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#define PACKET_SIZE 256
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#endif
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